van Damme Mireille, Zeilmaker Tieme, Elberse Joyce, Andel Annemiek, de Sain-van der Velden Monique, van den Ackerveken Guido
Plant-Microbe Interactions, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands.
Plant Cell. 2009 Jul;21(7):2179-89. doi: 10.1105/tpc.109.066811. Epub 2009 Jul 21.
Plant disease resistance is commonly triggered by early pathogen recognition and activation of immunity. An alternative form of resistance is mediated by recessive downy mildew resistant 1 (dmr1) alleles in Arabidopsis thaliana. Map-based cloning revealed that DMR1 encodes homoserine kinase (HSK). Six independent dmr1 mutants each carry a different amino acid substitution in the HSK protein. Amino acid analysis revealed that dmr1 mutants contain high levels of homoserine that is undetectable in wild-type plants. Surprisingly, the level of amino acids downstream in the aspartate (Asp) pathway was not reduced in dmr1 mutants. Exogenous homoserine does not directly affect pathogen growth but induces resistance when infiltrated in Arabidopsis. We provide evidence that homoserine accumulation in the chloroplast triggers a novel form of downy mildew resistance that is independent of known immune responses.
植物抗病性通常由早期病原体识别和免疫激活引发。另一种抗性形式由拟南芥中的隐性霜霉病抗性1（dmr1）等位基因介导。基于图谱的克隆表明，DMR1编码高丝氨酸激酶（HSK）。六个独立的dmr1突变体在HSK蛋白中各自携带不同的氨基酸取代。氨基酸分析表明，dmr1突变体含有高水平的高丝氨酸，而野生型植物中则无法检测到。令人惊讶的是，天冬氨酸（Asp）途径下游的氨基酸水平在dmr1突变体中并未降低。外源高丝氨酸不会直接影响病原体生长，但在拟南芥中浸润时会诱导抗性。我们提供的证据表明，叶绿体中高丝氨酸的积累引发了一种新型的霜霉病抗性，该抗性独立于已知的免疫反应。
